package com.example.yskjproject.view;
 
import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
 
import androidx.recyclerview.widget.RecyclerView;
import androidx.recyclerview.widget.StaggeredGridLayoutManager;


import com.tencent.cloud.tuikit.roomkit.BuildConfig;

import java.lang.reflect.Field;
 
/**
 * @descride 解决Scrollview中嵌套RecyclerView实现瀑布流时无法显示的问题，同时修复了子View显示时底部多出空白区域的问题
 */
public class FullyStaggeredGridLayoutManager extends StaggeredGridLayoutManager {
    private static boolean canMakeInsetsDirty = true;
    private static Field insetsDirtyField = null;
 
    private static final int CHILD_WIDTH = 0;
    private static final int CHILD_HEIGHT = 1;
    private static final int DEFAULT_CHILD_SIZE = 100;
    private int spanCount = 0;
 
    private final int[] childDimensions = new int[2];
    private int[] childColumnDimensions;
 
    private int childSize = DEFAULT_CHILD_SIZE;
    private boolean hasChildSize;
    private final Rect tmpRect = new Rect();
 
    public FullyStaggeredGridLayoutManager(Context context, AttributeSet attrs, int defStyleAttr,
                                           int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }
 
    public FullyStaggeredGridLayoutManager(int spanCount, int orientation) {
        super(spanCount, orientation);
        this.spanCount = spanCount;
    }
 
    public static int makeUnspecifiedSpec() {
        return View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);
    }
 
    @Override
    public void onMeasure(RecyclerView.Recycler recycler, RecyclerView.State state, int widthSpec,
                          int heightSpec) {
        final int widthMode = View.MeasureSpec.getMode(widthSpec);
        final int heightMode = View.MeasureSpec.getMode(heightSpec);
 
        final int widthSize = View.MeasureSpec.getSize(widthSpec);
        final int heightSize = View.MeasureSpec.getSize(heightSpec);
 
        final boolean hasWidthSize = widthMode != View.MeasureSpec.UNSPECIFIED;
        final boolean hasHeightSize = heightMode != View.MeasureSpec.UNSPECIFIED;
 
        final boolean exactWidth = widthMode == View.MeasureSpec.EXACTLY;
        final boolean exactHeight = heightMode == View.MeasureSpec.EXACTLY;
 
        final int unspecified = makeUnspecifiedSpec();
 
        if (exactWidth && exactHeight) {
            // in case of exact calculations for both dimensions let's use default "onMeasure" implementation
            super.onMeasure(recycler, state, widthSpec, heightSpec);
            return;
        }
 
        final boolean vertical = getOrientation() == VERTICAL;
 
        initChildDimensions(widthSize, heightSize, vertical);
 
        int width = 0;
        int height = 0;
 
        // it's possible to get scrap views in recycler which are bound to old (invalid) adapter entities. This
        // happens because their invalidation happens after "onMeasure" method. As a workaround let's clear the
        // recycler now (it should not cause any performance issues while scrolling as "onMeasure" is never
        // called whiles scrolling)
        recycler.clear();
 
        final int stateItemCount = state.getItemCount();
        final int adapterItemCount = getItemCount();
 
        childColumnDimensions = new int[adapterItemCount];
        // adapter always contains actual data while state might contain old data (f.e. data before the animation is
        // done). As we want to measure the view with actual data we must use data from the adapter and not from  the
        // state
        for (int i = 0; i < adapterItemCount; i++) {
            if (vertical) {
                if (!hasChildSize) {
                    if (i < stateItemCount) {
                        // we should not exceed state count, otherwise we'll get IndexOutOfBoundsException. For such items
                        // we will use previously calculated dimensions
                        measureChild(recycler, i, widthSize, unspecified, childDimensions);
                    } else {
                        logMeasureWarning(i);
                    }
                }
                childColumnDimensions[i] = childDimensions[CHILD_HEIGHT];
                //height += childDimensions[CHILD_HEIGHT];
                if (i == 0) {
                    width = childDimensions[CHILD_WIDTH];
                }
                if (hasHeightSize && height >= heightSize) {
                    break;
                }
            } else {
                if (!hasChildSize) {
                    if (i < stateItemCount) {
                        // we should not exceed state count, otherwise we'll get IndexOutOfBoundsException. For such items
                        // we will use previously calculated dimensions
                        measureChild(recycler, i, unspecified, heightSize, childDimensions);
                    } else {
                        logMeasureWarning(i);
                    }
                }
                width += childDimensions[CHILD_WIDTH];
                if (i == 0) {
                    height = childDimensions[CHILD_HEIGHT];
                }
                if (hasWidthSize && width >= widthSize) {
                    break;
                }
            }
        }
 
        int[] maxHeight = new int[spanCount];
        for (int i = 0; i < adapterItemCount; i++) {
            int position = i % spanCount;
            if (i < spanCount) {
                maxHeight[position] += childColumnDimensions[i];
            } else if (position < spanCount) {
                int mixHeight = maxHeight[0];
                int mixPosition = 0;
                for (int j = 0; j < spanCount; j++) {
                    if (mixHeight > maxHeight[j]) {
                        mixHeight = maxHeight[j];
                        mixPosition = j;
                    }
                }
                maxHeight[mixPosition] += childColumnDimensions[i];
            }
        }
 
        for (int i = 0; i < spanCount; i++) {
            for (int j = 0; j < spanCount - i - 1; j++) {
                if (maxHeight[j] < maxHeight[j + 1]) {
                    int temp = maxHeight[j];
                    maxHeight[j] = maxHeight[j + 1];
                    maxHeight[j + 1] = temp;
                }
            }
        }
        height = maxHeight[0];//this is max height
 
        if (exactWidth) {
            width = widthSize;
        } else {
            width += getPaddingLeft() + getPaddingRight();
            if (hasWidthSize) {
                width = Math.min(width, widthSize);
            }
        }
 
        if (exactHeight) {
            height = heightSize;
        } else {
            height += getPaddingTop() + getPaddingBottom();
            if (hasHeightSize) {
                height = Math.min(height, heightSize);
            }
        }
 
        setMeasuredDimension(width, height);
    }
 
    private void logMeasureWarning(int child) {
        if (BuildConfig.DEBUG) {
            Log.w("LinearLayoutManager", "Can't measure child #"
                    + child
                    + ", previously used dimensions will be reused."
                    + "To remove this message either use #setChildSize() method or don't run RecyclerView animations");
        }
    }
 
    private void initChildDimensions(int width, int height, boolean vertical) {
        if (childDimensions[CHILD_WIDTH] != 0 || childDimensions[CHILD_HEIGHT] != 0) {
            // already initialized, skipping
            return;
        }
        if (vertical) {
            childDimensions[CHILD_WIDTH] = width;
            childDimensions[CHILD_HEIGHT] = childSize;
        } else {
            childDimensions[CHILD_WIDTH] = childSize;
            childDimensions[CHILD_HEIGHT] = height;
        }
    }
 
    @Override public void setOrientation(int orientation) {
        // might be called before the constructor of this class is called
        //noinspection ConstantConditions
        if (childDimensions != null) {
            if (getOrientation() != orientation) {
                childDimensions[CHILD_WIDTH] = 0;
                childDimensions[CHILD_HEIGHT] = 0;
            }
        }
        super.setOrientation(orientation);
    }
 
    public void clearChildSize() {
        hasChildSize = false;
        setChildSize(DEFAULT_CHILD_SIZE);
    }
 
    public void setChildSize(int childSize) {
        hasChildSize = true;
        if (this.childSize != childSize) {
            this.childSize = childSize;
            requestLayout();
        }
    }
 
    private void measureChild(RecyclerView.Recycler recycler, int position, int widthSize,
                              int heightSize, int[] dimensions) {
        final View child;
        try {
            child = recycler.getViewForPosition(position);
        } catch (IndexOutOfBoundsException e) {
            if (BuildConfig.DEBUG) {
                Log.w("LinearLayoutManager",
                        "LinearLayoutManager doesn't work well with animations. Consider switching them off",
                        e);
            }
            return;
        }
 
        final RecyclerView.LayoutParams p = (RecyclerView.LayoutParams) child.getLayoutParams();
 
        final int hPadding = getPaddingLeft() + getPaddingRight();
        final int vPadding = getPaddingTop() + getPaddingBottom();
 
        final int hMargin = p.leftMargin + p.rightMargin;
        final int vMargin = p.topMargin + p.bottomMargin;
 
        // we must make insets dirty in order calculateItemDecorationsForChild to work
        makeInsetsDirty(p);
        // this method should be called before any getXxxDecorationXxx() methods
        calculateItemDecorationsForChild(child, tmpRect);
 
        final int hDecoration = getRightDecorationWidth(child) + getLeftDecorationWidth(child);
        final int vDecoration = getTopDecorationHeight(child) + getBottomDecorationHeight(child);
 
        final int childWidthSpec =
                getChildMeasureSpec(widthSize, hPadding + hMargin + hDecoration, p.width,
                        canScrollHorizontally());
        final int childHeightSpec =
                getChildMeasureSpec(heightSize, vPadding + vMargin + vDecoration, p.height,
                        canScrollVertically());
 
        child.measure(childWidthSpec, childHeightSpec);
 
        dimensions[CHILD_WIDTH] = getDecoratedMeasuredWidth(child) + p.leftMargin + p.rightMargin;
        dimensions[CHILD_HEIGHT] = getDecoratedMeasuredHeight(child) + p.bottomMargin + p.topMargin;
 
        // as view is recycled let's not keep old measured values
        makeInsetsDirty(p);
        recycler.recycleView(child);
    }
 
    private static void makeInsetsDirty(RecyclerView.LayoutParams p) {
        if (!canMakeInsetsDirty) {
            return;
        }
        try {
            if (insetsDirtyField == null) {
                insetsDirtyField = RecyclerView.LayoutParams.class.getDeclaredField("mInsetsDirty");
                insetsDirtyField.setAccessible(true);
            }
            insetsDirtyField.set(p, true);
        } catch (NoSuchFieldException e) {
            onMakeInsertDirtyFailed();
        } catch (IllegalAccessException e) {
            onMakeInsertDirtyFailed();
        }
    }
 
    private static void onMakeInsertDirtyFailed() {
        canMakeInsetsDirty = false;
        if (BuildConfig.DEBUG) {
            Log.w("LinearLayoutManager",
                    "Can't make LayoutParams insets dirty, decorations measurements might be incorrect");
        }
    }
}